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Allicin
| Section2 = }} . It was first isolated and studied in the laboratory by Chester J. Cavallito and John Hays Bailey in 1944. Eric Block, "Garlic and Other Alliums: The Lore and the Science" (Cambridge: Royal Society of Chemistry, 2010) This colorless liquid has a distinctively pungent smell. This compound exhibits antibacterial and anti-fungal properties. Allicin is garlic's defense mechanism against attacks by pests.What is Allicin? | |'大蒜素'（Allicin）是从葱科葱属植物大蒜（''Allium Sativum''）的鳞茎（大蒜头）中提取的一种有机硫化合物，也存在于洋葱和其他葱科植物中。学名二烯丙基硫代亚磺酸酯。 }} Structure and occurrence Allicin features the thiosulfinate functional group, R-S(O)-S-R. The compound is not present in garlic unless tissue damage occurs, and is formed by the action of the enzyme alliinase on alliin. Allicin is chiral but occurs naturally only as a racemate. The racemic form can also be generated by oxidation of diallyl disulfide:R. J. Cremlyn “An Introduction to Organosulfur Chemistry” John Wiley and Sons: Chichester (1996). ISBN 0 471 95512 4. :(SCH2CH=CH2)2 + RCO3H → CH2=CHCH2S(O)SCH2CH=CH2 + RCO2H Alliinase is irreversibly deactivated below a pH of 3; as such, allicin is generally not produced in the body from the consumption of fresh or powdered garlic.Brodnitz, M.H. Pascale, J.V., and Derslice, L.V. Flavor components of garlic extract. J. Agr. Food. Chem. 19(2):273-275, 1971 Furthermore, allicin can be unstable, breaking down within 16 h at 23 °C. 性质 大蒜素为淡黄色油状液体。具有强烈的大蒜臭、味辣。不溶于水，与乙醇、乙醚、苯、氯仿互溶。水溶液呈微酸性。对酸稳定，对热碱不稳定。蒸馏时分解。静置时有油状沉淀物产生。不稳定，23°C时可在16小时内分解。 生产 一般从大蒜的鳞茎（大蒜头）中提取，也可通过化学方法合成。用间氯过氧苯甲酸氧化二烯丙基二硫醚可得外消旋大蒜素。 1944年首先由 Cavallito 分离出来。 产生 一般认为，大蒜素的产生过程是大蒜粉碎后它所含的不稳定的蒜氨酸 (1)经蒜氨酶分解为烯丙次磺酸 (2)和脱氢丙氨酸 (3)， : 然后不稳定的脱氢丙氨酸 (3)立即分解为丙酮酸和氨，而烯丙次磺酸 (2)则两分子歧化为烯丙亚磺酸 (4)与烯丙硫醇 (5)，它们继续失水生成大蒜素 (6)： : 大蒜形成风味的机理与葱头十分相似，但粉碎过程中不会生成具有催泪性的中间体硫丙醛-''S''-氧化物。大蒜素对昆虫和微生物有一定的毒性，它的产生是大蒜对于昆虫进攻的自我防御机制。 分解 大蒜素遇热分解为烯丙次磺酸 (3)和烯丙硫醛 (7)，后者在常温下发生Diels-Alder反应，二聚成3-乙烯基-1,2-二硫杂-5-环己烯 (8)和2-乙烯基-1,3-二硫杂-5-环己烯 (9)等。 大蒜素在水和油介质中的分解产物有二烯丙基硫醚（包括二烯丙基一硫醚、二烯丙基二硫醚、二烯丙基三硫醚、二烯丙基四硫醚等）、乙烯基二噻己烯和阿藿烯（Ajoene）等：Theodor Dingermann (Hrsg.), Rudolf Hänsel (Hrsg.) und Ilse Zündorf (Hrsg.): Pharmazeutische Biologie: Molekulare Grundlagen und klinische Anwendungen. Springer Verlag Berlin; 1. Auflage 2002; ISBN 3-540-42844-5; S. 62f. 代谢 在体内很快被吸收。在血液中分解为烯丙硫醇 (2)。后被SAM甲基化为烯丙基甲硫醚 (3)，从肺中排出。 一般认为大部分烯丙硫醇会被氧化为烯丙磺酸，类似于从半胱氨酸到牛磺酸的转化过程。 功效 研究显示大蒜素有抗菌 、抗真菌、消炎、抗氧化 、抗血栓 、降血压 、维持脂蛋白平衡、防治动脉硬化 等功效。2009年，Vaidya、Ingold 和 Pratt 的研究表明大蒜素的生物功效主要是由大蒜素分解产生的2-丙烯次磺酸造成的，该化合物不稳定，很快便与体内的自由基发生反应使之失活。 用途 用作广谱抗菌药、饲料添加剂、杀虫剂和杀菌剂。 Potential health benefits Several animal studies published between 1995 and 2005 indicate that allicin may: reduce atherosclerosis and fat deposition. , normalize the lipoprotein balance, decrease blood pressure , have anti-thrombotic and anti-inflammatory activities, and function as an antioxidant to some extent . Other studies have shown a strong oxidative effect in the gut that can damage intestinal cells. A randomized clinical trial funded by the National Institutes of Health (NIH) in the United States and published in the Archives of Internal Medicine in 2007 found that the consumption of garlic in any form did not reduce blood cholesterol levels in patients with moderately high baseline cholesterol levels. The fresh garlic used in this study contained substantial levels of allicin so this study casts doubt on the ability of allicin when taken orally to reduce blood cholesterol levels in human subjects. In 2009, Vaidya, Ingold, and Pratt have clarified exactly how allicin works to produce its medicinal effects, such as trapping damaging radicals. According to them, it is the sulfenic acid, which is produced by the decomposition of allicin, that extremely rapidly reacts with free radicals, and binds with them. "We suggest that the peroxyl-radical-trapping activity of garlic is primarily due to 2-propenesulfenic acid formed by the decomposition of allicin." In 2010, Block, Dane, Thomas and Cody used a mass spectrometer with a DART ion source to identify 2-propenesulfenic formed when garlic is cut or crushed and to demonstrate that this sulfenic acid has a lifetime of less than one second. Antibacterial activity The antibacterial activity of allicin was reviewed by Ankri and Mirelman in 1999. Due to the increasing prevalence of methicillin-resistant Staphylococcus aureus (MRSA) in hospitals and the community, there has been an urgent need for new agents that could be used to deal with these bacteria. In this connection, in 2004, Cutler and Wilson have studied the effect of allicin on these bacteria. They used a new stable, aqueous extract of allicin, and have achieved very promising results. Cutler and Wilson note that the use of a water-based extract of allicin stabilizes the allicin molecule. They note further that this may be due to the hydrogen bonding of water to the reactive oxygen atom in allicin; also, there may be water-soluble components in crushed garlic that destabilize the molecule. (Presumably, the dilution of these components in water helps to preserve the allicin molecule.) Cutler and Wilson tested allicin on 30 clinical isolates of MRSA that show a range of susceptibilities to mupirocin. Strains were tested using agar diffusion tests. Of the strains tested, 88% had minimum inhibitory concentrations for allicin liquids of 16 mg/L, and all strains were inhibited at 32 mg/L. Furthermore, 88% of clinical isolates had minimum bactericidal concentrations of 128 mg/L, and all were killed at 256 mg/L. Of these strains, 82% showed intermediate or full resistance to mupirocin. Also, Cutler and Wilson found that an aqueous cream of allicin was somewhat less effective than allicin liquid. At 500 mg/L, however, the cream was still active against all the organisms tested—which compares well with the 20 g/L mupirocin currently used for topical application. See also / Si osou / 參看 * 蒜胺酸/Alliin * 蒜胺酸酶/Alliinase *二烯丙基二硫 *二烯丙基三硫（大蒜新素） *Allyl isothiocyanate, the active piquant chemical in mustard, radishes, horseradish and wasabi *Capsaicin, the active piquant chemical in chile peppers *Piperine, the active piquant chemical in black pepper *''syn''-Propanethial-''S''-oxide, the chemical found in onions *List of phytochemicals in food References / Riförènses / 參考資料 External links / Ikstörnol liŋks / 外部連結 *Investigation of allicin use against superbugs, MRSA & VRE *Antimicrobial properties of allicin from garlic Category:植物化学成分 Category:有机硫化合物 Category:烯烃 Category:消炎药 Category:抗生素 Category:抗氧化剂 Category:葱属 Category:Phytochemicals Category:Organosulfur compounds Category:Alkenes Category:Anti-inflammatory agents Category:Antibiotics Category:Dietary antioxidants Category:Pungent flavors Category:Alliaceae Category:Allium Category:Garlic Category:Antifungals